Narrative:

During a local private pilot training flight in VMC conditions; we were performing several maneuvers. My student was demonstrating a power-off stall and was in the recovery phase of the maneuver. With power full; he recovered nicely and was beginning to level out at 5;500' MSL. When he went to pull power back to cruise power setting of 2;300 RPM; the throttle was loose and came right out of the dash with cable still attached. At that point; we realized we no longer would have control of our power plant and we were stuck with full power. We had leveled out and I leaned out the mixture just enough to keep the engine from red-lining. We briefly discussed our options and since we had no way of managing power effectively; we knew we may need to land long if cutting power over the runway or perform a power-off 180 approach. ZZZ1 was having its monthly [club] fly in and as an un-towered airport at its busiest time; we elected to head back to ZZZ as they have emergency services and the longest runway close to our location. We turned for ZZZ and began to squawk 7700 after just a little more troubleshooting. We grabbed ATIS and ran appropriate checklists for the approach and checked for an emergency checklist applicable. Upon contact with tower; they were super helpful and accommodating and issued a 'direct-to' clearance for us. We notified them of the problem and we were assigned a right downwind entry for 12R coming from the south of the airport environment; this was so we landing into the wind of 7kts to help reduce the residual airspeed we would have do to the power setting. They asked if I was going to keep power on and cut it over the runway; but my concern was; since in level flight we were already exceeding Vn0 by about 15KIAS; in a descent I would pick up too much airspeed for structural safety or that would allow adequate maneuvering. So I elected to cut my power in the downwind leg when I was abeam the desired touchdown point and to perform a modified power-off 180 landing. When I was abeam; I reduced the mixture almost entirely to the shutoff position and lost all engine power. Then I proceeded inbound on the maneuver; and when I was certain of making the runway; I pulled the mixture completely out and began running; executing the appropriate checklist for an engine out landing. I was able to touchdown safely on the runway and was assisted by emergency services and my company for a tow back to the ramp.

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Original NASA ASRS Text

Title: C172 flight instructor reported a failure of the throttle control led to a diversion and intentional engine out approach for landing.

Narrative: During a local Private Pilot training flight in VMC conditions; we were performing several maneuvers. My student was demonstrating a power-off stall and was in the recovery phase of the maneuver. With power full; he recovered nicely and was beginning to level out at 5;500' MSL. When he went to pull power back to cruise power setting of 2;300 RPM; the throttle was loose and came right out of the dash with cable still attached. At that point; we realized we no longer would have control of our power plant and we were stuck with full power. We had leveled out and I leaned out the mixture just enough to keep the engine from red-lining. We briefly discussed our options and since we had no way of managing power effectively; we knew we may need to land long if cutting power over the runway or perform a power-off 180 approach. ZZZ1 was having its monthly [Club] fly in and as an un-towered airport at its busiest time; we elected to head back to ZZZ as they have emergency services and the longest runway close to our location. We turned for ZZZ and began to squawk 7700 after just a little more troubleshooting. We grabbed ATIS and ran appropriate checklists for the approach and checked for an emergency checklist applicable. Upon contact with tower; they were super helpful and accommodating and issued a 'direct-to' clearance for us. We notified them of the problem and we were assigned a right downwind entry for 12R coming from the South of the airport environment; this was so we landing into the wind of 7kts to help reduce the residual airspeed we would have do to the power setting. They asked if I was going to keep power on and cut it over the runway; but my concern was; since in level flight we were already exceeding Vn0 by about 15KIAS; in a descent I would pick up too much airspeed for structural safety or that would allow adequate maneuvering. So I elected to cut my power in the downwind leg when I was abeam the desired touchdown point and to perform a modified power-off 180 landing. When I was abeam; I reduced the mixture almost entirely to the shutoff position and lost all engine power. Then I proceeded inbound on the maneuver; and when I was certain of making the runway; I pulled the mixture completely out and began running; executing the appropriate checklist for an engine out landing. I was able to touchdown safely on the runway and was assisted by emergency services and my company for a tow back to the ramp.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.